The field of the invention is generally that of honing and grinding, and, more particularly, that of the honing and grinding of curved exterior workpiece surfaces and, especially, and more particularly, with respect to centerless honing or grinding arrangements for such curved external workpiece surfaces. Certain prior art centerless grinding constructions have been developed in the past and have employed three wheels or cylinders triangularly mounted with respect to each other so as to have a grinding space between the three grinding wheels or cylinders where a part which is to be ground or shaped is effectively placed at a location substantially at the center of the triangular shape defined by the three grinding wheels or cylinders. In such a prior art centerless grinder construction, one of the wheels or cylinders is normally made of rubber or the like and is used as the driving mechanism to rotate the workpiece which is to be ground and which is held in the so-called "centerless fashion" by the other two wheels or cylinders which are normally hard and brittle grinding wheels of various lengths, sizes and grinding grit composition. If a part is to be shaped, then the opposing shape is ground into one of the abrasive wheels so that the grinding of the workpiece or part will effectively be a form of abrasive machining of the part down to its proper size and shape. In this type of arrangement, the other wheel is an abrasive wheel operated under power and it operates to apply pressure and to aid in the grinding.
One of the major disadvantages of a prior art centerless grinder of the type referred to above arises primarily from the fact that the abrasive grinding wheels are usually constructed of a very rigid, relatively brittle material which not only has a chance to break during usage because of its brittleness, but which also tends to wear down and modify the grinding contact thereof with a workpiece unless such wear is fully compensated for and, further, and most important, is the fact that such a prior art type of rigid stone grinding (or effective machining by such grinding action) of a workpiece develops what can be referred to as a "peaky" finish having a multitude of cut, torn, and folded metal portions which become very evident when viewed by a scanning electron microscope and as is best evidenced by such scanning electron miscroscopic pictures. In addition, any steps or recesses in such a prior art workpiece will normally have very sharp edges which, under normal operating conditions, will need to be radiused or deburred.
Such a "peaky" finish, produced by prior art centerless grinders is one where the peaks and valleys, which are the customary micro-profile configuration of such a metal workpiece surface, are area co-extensive with most of the projected surface area of the workpiece--that is, most of any given portion of such a workpiece surface area consists of peaks and valleys, which is highly undesirable when the workpiece surface is intended to movably coact with another abutting workpiece surface, such as in a piston and cylinder (or piston ring around a piston and an adjacent cylinder wall), in a bearing and journal, or the like. The initial "peaky" finish of two such new abutting metal surfaces is the reason for the conventionally required so-called "break-in period" for such new coacting parts. The present inventor has found that if such abutting coacting metal parts are surface-finished with what the present inventor terms a plateaued finish, by which is meant a finish where a substantial portion of the micro-profile peaks of each metal surface, as seen in cross-section, are honed off so as to leave a multitude of such substantially flat or plateaued tops, with a substantial portion of the complete projected area of that part of the surface being comprised of such plateaued tops. When each movably coacting, slideably abutting, metal surface of any apparatus of the type referred to above is of such plateaued surface finish configuration, there is no initial "break-in" required for the apparatus and virtually no damage to the adjacent metal surfaces will occur during even heavy or high-load or high-torque initial operating conditions, such as very frequently occurs in prior art constructions of the type mentioned above having conventionally finished coacting metal surfaces which are of the "peaky" type mentioned above.
It is obvious that it would be highly desirable to provide a honing apparatus of the so-called "centerless" type which would produce such a plateaued finish on a workpiece, and it is precisely such highly desirable and advantageous type of external honing apparatus which is provided by, and in, the present invention and which has advantages of the desirable type either explicit or implicit in the foregoing comments which will readily produce a plateaued surface on a workpiece, thus, virtually completely overcoming the problems, disadvantages and limitations of the above-mentioned type of prior art centerless grinders, and wherein all of the advantages flow from, and occur by reason of, the specific features of the invention pointed out hereinafter and primarily because of the extreme1y flexible and self-centering mounting of the abrasive particles.